JP5661576B2 - Uninterruptible power supply system - Google Patents

Description

  The present invention relates to an uninterruptible power supply system capable of continuing to supply stable power to a load even when a commercial power supply becomes abnormal.

  Since the conventional uninterruptible power supply is designed on the assumption that power is always supplied to the rated load, the efficiency tends to decrease at a light load of 60% or less, for example. For this reason, in a parallel connection type uninterruptible power supply system in which a plurality of uninterruptible power supply devices (hereinafter referred to as UPS) are connected in parallel to supply power to a load, a predicted load pattern and a reference value are set. An uninterruptible power supply system has been proposed that predicts the continuity of the relationship and determines the required number of operating units for the time being, and as a result, operates only the required number of operating units and stops unnecessary UPS. See 1.)

Japanese Patent Publication No.51-12458 (Overall)

  In the uninterruptible power supply system shown in Patent Document 1, when the load current is small, the loss generated in the inverter part of the UPS can be suppressed, but the converter part needs to be charged with the storage battery, so the inverter part Even if the operation was stopped, it was necessary to continue the operation. In addition, if the converter is stopped to further improve operating efficiency, the storage battery cannot be charged, and if this takes a long time, the storage battery will deteriorate due to overdischarge due to a minute current, and will not recover even if charged. There was a problem.

  The present invention has been made to solve the above-described problems. When the load current is small, the converter is stopped as well as the inverter, and at the same time, the uninterruptible power can be charged at the required time. An object is to provide a power supply system.

In order to achieve the above object, an uninterruptible power supply system of the present invention includes a converter that converts an AC voltage input from a commercial power source into a DC voltage, and an inverter that converts the output of the converter into an AC voltage again and outputs it. And a plurality of uninterruptible power supply units whose outputs are connected in parallel with each other to supply power to the load, storage batteries respectively connected to the output side of each converter, and input current of the load are detected A load current detector; and a calculation control means for giving an operation / stop command to the plurality of uninterruptible power supply apparatuses, wherein the calculation control means is configured to output the uninterruptible power supply apparatus when the load current is a predetermined value or less. at least one converter and the inverter stops operation, the connected battery to the uninterruptible power supply was stopped, due to the loss of charge function by stopping the converter So as not to discharge a predetermined amount or more, it is characterized by having over-discharge preventing means so as to switch the uninterruptible power supply shutdown sequence.

  According to the present invention, it is possible to provide an uninterruptible power supply system capable of charging not only the inverter but also the converter when the load current is small, and at the same time charging the storage battery.

The block block diagram of the uninterruptible power supply system which concerns on Example 1 of this invention. The operation | movement flowchart of the uninterruptible power supply system which concerns on Example 1 of this invention. The block block diagram of the uninterruptible power supply system which concerns on Example 2 of this invention. The operation | movement flowchart of the uninterruptible power supply system which concerns on Example 2 of this invention. The block block diagram of the uninterruptible power supply system which concerns on Example 3 of this invention. The operation | movement flowchart of the uninterruptible power supply system which concerns on Example 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, an uninterruptible power supply system according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows an example in which three UPSs, UPS 11 (No 1 UPS), UPS 12 (No 2 UPS) and UPS 13 (No 3 UPS) are provided.

  Each of the UPSs 11, 12, and 13 receives an AC voltage from the commercial power supply 1, and converts each into a DC voltage by each of the converters 11 a, 12 a, and 13 a via an AC input switch, and then again by the inverters 11 b, 12 b, and 13 b. The AC voltage is inversely converted, and the outputs are connected to each other so that a stable AC voltage is supplied to the common load 2. Further, the converters 11a, 12a, and 13a store DC energy in storage batteries provided corresponding to the respective UPSs via DC switches. For example, when a power failure occurs in the commercial power source 1, the DC energy of each storage battery is stored. Is supplied to inverters 11b, 12b, and 13b, respectively, to continuously output an AC voltage.

  In addition, even if a failure occurs in the converters 11a, 12a, 13a or the inverters 11b, 12b, 13b, the alternating current is continuously fed from the same or different bypass power supply as the commercial power supply 1 in order to continuously output the alternating current. In some cases, a bypass circuit is provided, but the illustration is omitted here.

  The current flowing into the load 2 is detected by the current detector 21 and given to the digital arithmetic circuit 31 via the AD converter 22. The digital arithmetic circuit 31 is arithmetic means for managing the operation of the entire uninterruptible power supply system. The digital arithmetic circuit 31 outputs an operation / stop command to the UPS 11, 12, 13 and obtains an operation state signal from the UPS 11, 12, 13. ing.

  Next, the operation will be described. FIG. 2 is an operation flowchart of the uninterruptible power supply system according to the first embodiment of the present invention, and shows an operation flow performed by the digital arithmetic circuit 31.

  First, start from a state where at least two of the three UPSs (UPS 11, 12, 13) are operating in parallel. Then, it is determined whether or not the load current is 50% or less (step ST1), and in the case of YES, it is determined whether or not the stop time of No1 UPS (UPS11) exceeds the specified time (step ST2). If the specified time is exceeded, No1 UPS (UPS11) is operated, and No2 UPS (UPS12) is stopped (step ST3). Here, the stop of the UPS means that the operation of the converter is stopped in addition to the inverter. Therefore, when the UPS is stopped, charging to the storage battery is stopped. If the specified time is not exceeded in step ST2, it is determined whether the stop time of No2 UPS (UPS12) has exceeded the specified time (step ST4). If the specified time is exceeded, the No. 2 UPS (UPS 12) is operated and the No. 3 UPS (UPS 13) is stopped (step ST5). If the specified time is not exceeded in step ST4, it is determined whether the stop time of No3UPS (UPS13) has exceeded the specified time (step ST6). If the specified time is exceeded, the No. 3 UPS (UPS 13) is operated and the No. 1 UPS (UPS 11) is stopped (step ST7).

  If the specified time is not exceeded in step ST6, it is checked whether there is a UPS that has stopped (step ST8). If there is a UPS that has stopped, the state is maintained as it is, and if there is no UPS that has stopped. No1 UPS (UPS11) is stopped (step ST9). Steps ST8 and ST9 show an initial operation in which the load current becomes 50% or less for the first time from the state in which three units are in parallel operation.

  If the load current is less than 50% in step ST1, it is confirmed whether there is a UPS that is stopped (step ST10). If there is no UPS that is stopped, the state is maintained and there is no UPS that is stopped. If there is, the UPS that is stopped is determined (step ST11), and an operation command is given to the UPS (ST12).

  By repeating the above steps ST1 to ST12 at a predetermined sampling cycle, the UPS stop period is preferably set to a predetermined period (in the case of three UPS units, it is preferably set to about ½ of the charging inverter of the storage battery. ) Is operated preferentially, and the UPS of the next unit is stopped instead. When the UPS stop period exceeds a predetermined period, the corresponding UPS is sequentially activated and the UPS of the next unit is stopped. As a result, it is possible to reduce the loss of the converter during the UPS stop period to substantially zero while automatically charging each UPS storage battery sequentially, and to improve the operation efficiency of the system. The predetermined period is usually set to a period shorter than the period for preventing the UPS from being overdischarged. Here, the function of switching the sequentially stopped UPS is referred to as overdischarge prevention means.

  Hereinafter, an uninterruptible power supply system according to Embodiment 2 of the present invention will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a block diagram of an uninterruptible power supply system according to Embodiment 3 of the present invention. About each part of this Example 2, the same part as each part of the uninterruptible power supply system which concerns on Example 1 of this invention of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The difference between the second embodiment and the first embodiment is that the voltage of the storage battery connected to each UPS is detected and this storage battery voltage is supplied to the digital arithmetic circuit 31A via the AD converter 23. is there.

  FIG. 4 is an operation flowchart of the uninterruptible power supply system according to the second embodiment of the present invention, and shows an operation flow performed by the digital arithmetic circuit 31A. About each part of this flowchart, the part same as each part of the operation | movement flowchart of the uninterruptible power supply system which concerns on Example 1 of this invention of FIG. 2 is shown with the same code | symbol, and the description is abbreviate | omitted. The difference between the second embodiment and the first embodiment is that "determination of whether or not the stop time of No1UPS (UPS11) exceeds the specified time" in step ST2 is that the storage battery voltage of No1UPS (UPS11) is lower than the specified value in step ST2A. Similarly, with respect to the points replaced with “determination of whether or not,” STST and ST6, “determination of whether or not the storage battery voltage of No2UPS (UPS12) is less than the specified value” shown in steps ST4A and ST6A, respectively. This is a point replaced with “determination of whether or not the storage battery voltage of No3UPS (UPS13) has become less than a specified value”.

  In Example 1, the discharge of the storage battery was predicted based on the stop time, but in Example 2, the voltage of the storage battery was measured and it was determined whether it was time to charge. As a result, even when the discharge characteristics of the storage battery change due to changes in the ambient temperature, changes in the minute discharge current, etc., it is possible to charge with the optimum charging inverter valve. The voltage of the storage battery is preferably detected with some impedance, that is, with some discharge current flowing.

  Hereinafter, an uninterruptible power supply system according to Embodiment 3 of the present invention will be described with reference to FIGS. 5 and 6.

  FIG. 5 is a block diagram of an uninterruptible power supply system according to Embodiment 3 of the present invention. About each part of this Example 3, the same part as each part of the uninterruptible power supply system which concerns on Example 2 of this invention of FIG. 3 is shown with the same code | symbol, and the description is abbreviate | omitted. The third embodiment is different from the second embodiment in that a voltage detector 24 for detecting the voltage of the commercial power source 1 is provided and this detected voltage is applied to the digital arithmetic circuit 31B via the AD converter 25. is there.

  Considering the case where a long-time power failure occurs in Example 1 or Example 2, all the storage batteries are in a discharged state. In such a case, even if the load current at the time of power recovery is 50% or less, the UPS should not be stopped and the storage battery should be given priority.

FIG. 6 is an operation flowchart of the uninterruptible power supply system according to the third embodiment of the present invention, and shows an operation flow of the digital arithmetic circuit 31B based on the above concept. About each part of this flowchart, the part same as each part of the operation | movement flowchart of the uninterruptible power supply system which concerns on Example 2 of this invention of FIG. 4 is shown with the same code | symbol, and the description is abbreviate | omitted. The difference between the third embodiment and the second embodiment is that when the load current is 50% or less in step ST1, the process does not immediately shift to step ST2A, but moves to step ST2A when there is no storage battery discharged due to a power failure. If there is a storage battery, a series of steps ST13 to ST18 is added in which the storage battery is transferred to a charging flow. Hereinafter, the contents of steps ST13 to ST18 will be described.

  When the load current is less than 50% in step ST1, it is determined whether or not an input power failure has occurred within a predetermined period (step ST13). If there is no power failure, the process goes to step ST2A, and the process proceeds to the same flow as in the second embodiment. If “YES” in step ST13, the discharge amount of the storage battery is obtained from the power failure period stored in the digital arithmetic circuit and the transition of the load current in that period (step ST14). Next, it is determined whether or not the discharge amount is greater than or equal to a specified value (step ST15). If the discharge amount is less than the specified value in step ST15, the process goes to step ST2A, and the process proceeds to the same flow as in the second embodiment. When the discharge amount is equal to or greater than the specified value in step ST15, it is determined whether or not there is a stop UPS (step ST16). In addition, since the operation by the storage battery when there is a normal power outage operates all the UPSs regardless of the load state, whether or not there is a stop UPS here is stopped within a predetermined period before the occurrence of the power outage. It means whether there was a UPS. If there is a UPS that has been stopped, the UPS is determined (step ST17), the stopped UPS is forcibly operated for a predetermined period (for example, 24 hours) (step ST18), and the storage battery is charged. If there is no UPS stopped in step ST16, the state is left as it is.

  If the load current is 50% or more in step ST1, the process proceeds to the flow after step 10 as in the second embodiment.

  As described above, according to the third embodiment, even when a power outage occurs for a long time, the discharge status of the storage battery is confirmed, and the UPS that is considered to be preferentially required to be charged is continuously forced. Since the battery is charged, the specified power failure compensation time can be secured even if a power failure occurs again.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, in the embodiment, the configuration of three UPSs has been described, but any number of UPSs may be used as long as it is two or more. The parallel system of a plurality of UPSs may or may not constitute a parallel redundant system. That is, the present invention can be applied to any system in which the number of operating units is reduced in order to improve the operating efficiency when the load current becomes a predetermined value or less in a parallel system. Further, the third embodiment has been described as an example combined with the second embodiment. However, steps ST2A, ST4A and ST6A in FIG. 6 may be replaced with ST2, ST4 and ST6, respectively, and combined with the first embodiment. Further, in the second embodiment, the protection that does not lead to overdischarge is performed by detecting the voltage of the storage battery, but other methods using a discharge current, a charging current, or the like can also be adopted.

1 Commercial power supply 2 Load 11 1UPS
12 No. 2UPS
13 No. 3UPS
11a, 12a, 13a Converter 11b, 12b, 13b Inverter 21 Load current detector 22, 23, 25 AD converter 24 Voltage detector 31, 31A, 31B Digital arithmetic circuit

Claims (4)

Consists of a converter that converts AC voltage input from a commercial power source into DC voltage, and an inverter that converts the output of the converter into AC voltage again and outputs the output. Multiple uninterruptible power supplies
Storage batteries respectively connected to the output side of each converter,
A load current detector for detecting an input current of the load;
Computation control means for giving an operation / stop command to the plurality of uninterruptible power supply units,
The arithmetic control means includes
When the load current is less than or equal to a predetermined value, shut down at least one converter and inverter of the uninterruptible power supply,
Overdischarge prevention means for sequentially switching the uninterruptible power supply to be stopped so that the storage battery connected to the uninterruptible uninterruptible power supply does not discharge more than a predetermined amount due to loss of the charging function due to the stop of the converter An uninterruptible power supply system characterized by comprising: The overdischarge prevention means includes
2. The uninterruptible power supply system according to claim 1, wherein when the uninterruptible power supply is continuously stopped for a first predetermined period, the uninterruptible power supply to be stopped is sequentially switched. The overdischarge prevention means includes
The uninterruptible power supply system according to claim 1, wherein when the voltage of the storage battery connected to the uninterruptible power supply becomes equal to or lower than a predetermined value, the uninterruptible power supply to be stopped is sequentially switched. Voltage detecting means for detecting a power failure of the commercial power supply,
The arithmetic control means includes
When the commercial power is restored after a power failure for a second predetermined period,
From the transition of the load current during the power outage period, estimate the discharge amount of the storage battery,
When there is an uninterruptible power supply whose discharge amount is equal to or greater than a predetermined value and stopped within the third predetermined period before the power failure,
The uninterruptible power supply system according to any one of claims 1 to 3, wherein the uninterruptible power supply is forcibly continued for a fourth predetermined period.

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